52840 advertising data not received by certain Android devices

RE: 52840 advertising data not received by certain Android devices

Susheel Nuguru — Mon, 09 May 2022 06:46:12 GMT

The beacons are not required to have very strict timing in terms of their start time. There is also great tolerance in terms of adv delay of 0-10ms. If other phones are able to read the packets, then I assume that the transmission from the beacons are working fine.

I would still try to check the XTAL clocks accuracy you are using. do you observe that there can be any difference in these both?

Also, can you please setup an BLE air sniffer and sniff the packets of both 2025KR and 2045RN to see if there are any ambiguities in terms of timing of the packets? I still strongly suspect that this is something from the Android BLE stack implementations on the phones that are not able to receive this beacon packets and not on the nRF side.

RE: 52840 advertising data not received by certain Android devices

RickW — Thu, 05 May 2022 18:17:43 GMT

1) They are broadcasting at the same time, but it doesn't seem to have issues with iOS devices seeing both. Also, other Android devices are able to see both.

2) Yes, these are advertising packets

3) The only sniffer I have is on the receiver, where I captured the packets listed above. There are some differences in the packets sent

2025KR

00000000: 3E38 0D01 1326 01C3 DF6E B773 F081 00FF >8...&...n.s....
00000010: 7FDB 0000 0000 0000 0000 001E 0201 0502 ................
00000020: 0A08 0302 0001 07FF 564C 32C9 0002 0B09 ........VL2.....
00000030: 4C76 4274 6E20 6466 6333 LvBtn dfc3

2045RN

00000000: 3E38 0D01 1326 01FC 05C7 62D9 D781 00FF >8...&....b.....
00000010: 7FCC 0000 0000 0000 0000 001E 0201 0502 ................
00000020: 0A08 0302 0001 07FF 564C 32C9 0002 0B09 ........VL2.....
00000030: 4C76 4274 6E20 3035 6663 LvBtn 05fc

4) The LFCLK seems to be a no-name brand 32Khz. The same one is used on both PCBs, however I just noticed that on the PCB where it is not working, this 2-pin clock IC is reversed.

5) I tried 4 devices that use the 2025KR and 7 devices that use the 2045RN and all had the same behavior. All the 2025KR devices work and all the 2045RN devices don't

If there is a clock accuracy issue, I might be able to disable the low-frequency clock and see if it works. Could an issue with the high frequency clock also do something like this?

Thanks for the help

RE: 52840 advertising data not received by certain Android devices

Susheel Nuguru — Thu, 05 May 2022 17:35:18 GMT

That seems strange.

Are the two beacons transmitting at the same time? Is it possible that there are collisions? Are the advertising packets ?

Have you tested this with multiple 2045RN chips and the failing behavior is same on all?

Do you have a sniffer trace to check if the advertisement packet is being transmitted properly by the chips?

It is possible that the failing chip may have some clock accuracy issue. Can you specify which LFCLK you are using for your designs?